Potentiometer problem

crutschow

Joined Mar 14, 2008
38,503
35V applied to a 5kΩ pot will dissipate 0.245W, but there's no way you can draw 1A from the pot wiper, as that would be many watts of power.

You could add a transistor buffer to the pot output, if you want to draw that amount of current.
What output voltage do you want @ 1A current?
 

Thread Starter

geo1703

Joined Jun 1, 2024
16
For what purpose?

If you can figure out how to get 1A through 5K with 35V please let us know how.

Tell us what problem you are trying to solve.
The current and voltage supply are from the transformer(12 V and 1amp) and I already rectified it. I just want to change the potentiometer from 50k to 5k. Screenshot_20240603_004816.jpg
 

ThePanMan

Joined Mar 13, 2020
918
Lighting LED lights is not linear. A pot will give you a linear taper but the LED's will appear to hardly change in intensity. Your better bet is to use PWM, or Pulse Width Modulation. PWM modules are available on Amazon and many other sites. With PWM you get a full sweep of the brightness from full to dark. There's no need to build something unless your main goal is to learn something.

LED's are not voltage dependent, they are current dependent. You have to limit the amount of current through them in order to control them. Yes, a pot will do that. but the amount of power going through the pot will likely be way too great for it to withstand the amount of heat it has to dissipate. Again, PWM is your better option.
 

dl324

Joined Mar 30, 2015
18,326
What you drew makes no sense:
pot.jpg1717356487350.png
EDIT: just noticed that there could be a connection to ground for C1 and R1. That's bad.

You have C1 connected backwards (and I'm not sure why you need it). If you get it reverse biased by more than half a volt, bad things can happen.

You didn't show what the load is, but you'll have some current flowing in the pot because the collector-base junction will be forward biased.

You drew the transistor upside down; the emitter would usually be on the bottom. When they're used as a pass element, we usually draw them with the base pointing down as I've done.
 
Last edited:

WBahn

Joined Mar 31, 2012
32,823
is it ok to use 5k potentiometer on 35 volts and 1 amp current?
Depends on the potentiometer, but it is very unlikely that the one you have will survive long.

How are you planning to use the potentiometer? To get 1 A from 35 V, a DC resistance would need to be just 35 Ω, or less than 1% of your pot's end-to-end value.
 

Thread Starter

geo1703

Joined Jun 1, 2024
16
What you drew makes no sense:
View attachment 323736View attachment 323737
EDIT: just noticed that there could be a connection to ground for C1 and R1. That's bad.

You have C1 connected backwards (and I'm not sure why you need it). If you get it reverse biased by more than half a volt, bad things can happen.

You didn't show what the load is, but you'll have some current flowing in the pot because the collector-base junction will be forward biased.

You drew the transistor upside down; the emitter would usually be on the bottom. When they're used as a pass element, we usually draw them with the base pointing down as I've done.
Thank you for helping me, I'm already done making our project
 

Tonyr1084

Joined Sep 24, 2015
9,744
is it ok to use 5k potentiometer on 35 volts and 1 amp current?
One point that might need clearing up: You have a 35 volt power supply. It's capable of delivering up to 1 amp. That doesn't mean your circuit will draw, or be force fed 1 amp. The circuit will draw whatever amperage it will draw. Provided it doesn't draw more than 1 amp your circuit - ANY circuit - stands a chance of working properly. I'm not prognosticating that your circuit will work, I'm just clearing up the mistake a lot of newbie's make, assuming that if a PS can deliver 1 amp, or 10 amps or even a million amps that your circuit will be forced to run at that amperage. Ohm's law states that a given voltage and resistance will draw enough current (amperage) to run that circuit.

Think of it like a bucket of water. You're thirsty. You're only going to drink what you can handle and need. You don't have to drink the whole bucket of water. Same is true with basic electronics. If your circuit runs on 35 volts and has a resistance load of 100Ω then your circuit will only draw (35V ÷ 100Ω = 0.35 amps {or 350mA, that's Milli amps}). If your supply can't push 350mA then your circuit will fail.

Obviously there are problems with your circuit. I'm not chasing after figuring out what you're trying to do or how your circuit works (or doesn't work). Just wanted to point out that a PS (Power Supply) needs to be the proper voltage and sufficient amperage. The subject of PS's is another field of discussion altogether. We don't need to get into all that at this time.
 

ElectricSpidey

Joined Dec 2, 2017
3,334
Most of these "power supplies" and "voltage regulator" circuits you see on YouTube, are neither power supplies or regulators and are actually just power control circuits.

(simple adjustable follower circuits)
 
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